Finding Collections

I haven't been doing that much roll hunting but enough that I have been finding some odd things. I get batches where I think people have cached their collection in (or it was stolen). The reason I say this is because I'll open a roll and it will start with a 1970 coin, then 1971,1921, 1973, 1974, etc. All in pretty good condition too. I have been finding to many like this to be coincidence. Really, what are the odds that 50 coins in a roll will be lined up by date.
I guess that things are getting bad enough people are even cashing in their smaller collections.